Manual for the labour-based construction of bituminous surfacings on ...ed_emp/@emp_policy/@invest/... · Manual for the labour-based construction of bituminous surfacings on low-volume

Manual for the labour-basedconstruction of bituminoussurfacings on low-volume roads

TRL Limited Department for International DevelopmentOld Wokingham Road 1 Palace StreetCrowthorne, Berkshire, RG45 6AU London, SW1E 5HE

ii

First Published 2003ISBN 0-9543339-3-4Copyright TRL Limited 2003.

This document is an output from a project funded by the UKDepartment for International Development (DFID) for thebenefit of developing countries. The views expressed in it arenot necessarily those of the Department for InternationalDevelopment (DFID).

TRL is committed to optimising energy efficiency, reducingwaste and promoting recycling and re-use. In support of theseenvironmental goals, this report has been printed on recycledpaper, comprising 100% post-consumer waste, manufacturedusing a TCF (totally chlorine free) process.

Subsector: Transport

Theme: T2

Project title: Appropriate surfacings for low-volume roads

Project reference: R7470

iii

The Department for International Development: a brief mission statement

The Department for International Development (DFID) is the UK Government departmentresponsible for promoting sustainable development and reducing poverty. The centralfocus of the Government’s policy, based on the 1997 and 2000 White Papers onInternational Development, is a commitment to the internationally agreed MillenniumDevelopment Goals, to be achieved by 2015. These seek to:

� Eradicate extreme poverty and hunger

� Achieve universal primary education

� Promote gender equality and empower women

� Reduce child mortality

� Improve maternal health

� Combat HIV/AIDS, malaria and other diseases

� Ensure environmental sustainability

� Develop a global partnership for development

DFID’s assistance is concentrated in the poorest countries of sub-Saharan Africa and Asia,but also contributes to poverty reduction and sustainable development in middle-incomecountries, including those in Latin America and Eastern Europe.

DFID works in partnership with governments committed to the Millennium DevelopmentGoals, with civil society, the private sector and the research community. It also works withmultilateral institutions, including the World Bank, United Nations agencies, and theEuropean Commission.

DFID has headquarters in London and East Kilbride, offices in many developingcountries, and staff based in British embassies and high commissions around the world.

DFID, 1 Palace Street, London SW1E 5HE

DFID, Abercrombie House, Eaglesham Road, East Kilbride, Glasgow G75 8EA

Tel: +44 (0) 20 7023 0000

Fax: +44 (0) 20 7023 0019

Public Enquiry Point: 0845 300 4100 (from outside the UK: +44 1355 84 3132)

DFID website: www.dfid.gov.uk

Email: [email protected]

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ACKNOWLEDGEMENTS

This manual was produced in the International Division of TRL (DirectorMr S W Colwill) on behalf of the Department for International Development as part ofits ‘Knowledge and Research’ programme. The International Division wishes to thankThe National Roads Administration (ANE) of Mozambique and the staff of ScottWilson Consulting Engineers, Quelimane for their assistance and co-operation. TheTRL project team responsible for this manual was Mr W G Ford, Mr H R Smith,Mr C R Jones, Mr A C Edwards, Mr S Done and Mr P A K Greening. Where necessary,use has been made of work published by other research and road authorities.

TRL LimitedCrowthorneBerkshire, RG45 6AUUnited Kingdom

www.trl.co.uk

Limited extracts from the text may be reproduced provided the source isacknowledged. For more extensive reproduction, please contact TRL usingthe postal or website address above.

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CONTENTS

Page

1 Introduction 1

2 Choice of surfacing 1

2.1 Surface treatments 2

3 Materials for bituminous surfacings 6

3.1 Cut-back bitumens 6

3.2 Bitumen emulsions 6

3.3 Aggregates 7

4 Tools and equipment 8

4.1 Spraying by hand lance 12

5 Health and safety 14

6 Project organisation 15

6.1 Planning 15

6.2 Workforce 17

7 Preparation of existing road surface 18

7.1 Methods of preparation 22

7.1.1 Grading 22

7.1.2 Regravelling 24

7.1.3 Compaction 26

8 Priming 28

9 Sand seal 30

10 Slurry seal 32

11 Single surface dressing 36

12 Double surface dressing 48

13 Single Otta seal 52

14 Double Otta seal 56

Page

15 Pre-mixed bitumen and gravel 60

16 Penetration macadam 64

17 Maintenance 68

Appendix A: Worked examples 70

Appendix B: Design of surface dressing 83

Appendix C: Hand lance delivery spray rates 85

1

1 Introduction

This manual is a guide to the construction of new bituminous surfacings onunpaved low trafficked roads in tropical countries using labour-basedmethods. It is aimed at local government officials and their staff, and small-scale contractors who are responsible for carrying out the work employingmainly local labour.

To achieve the desired results it is essential that works supervisors be trained bymeans of short training courses and field trials to deliver the required standard ofworkmanship. This manual can also be used to assist with this training.

Labour-based construction of bituminous surfacings can be very effectiveproviding there is good roadside drainage and the underlying road surface issufficiently stable and the workmanship is to a good standard. It is thereforestressed that the preparation of the existing road and materials used must meetthe particular country and ministry design specifications before any sealingwork is undertaken.

Road construction in rural areas is increasingly being focused on provision ofaccess and poverty alleviation. When access is treated as a priority, it is likelythat there will be an increased use of spot improvement techniques. Thedecision to surface a road with a bituminous seal may be made because theexisting gravel pavement requires too much maintenance or because suitableregravelling materials are scarce and in some cases sealing roads, which carrytraffic as low as 30 vpd, may be justified. The upgrading of short sections ofroad for which the use of conventional large road construction equipment isprohibitively expensive make the methods described here most suitable.

The techniques described in this manual, use low cost plant that can either bemanufactured locally or be bought or hired by small local contractors.However, there are situations where traffic levels will be at the limit of the‘low-volume’ category and in these cases the use of bitumen heating andspraying tanks if appropriate, should be used. Any additional equipment thatmay be required should be relatively cheap and within the range of the capitalinvestment expected by small-scale contractors.

2 Choice of surfacingSeveral types of bituminous surfacings can be constructed by labour-basedmethods using small, affordable plant such as tractors, trailers, hand sprayers,concrete mixers and pedestrian rollers. Some can be constructed to acceptablestandards using the simplest of hand tools and materials. Although coldbitumen emulsion is the ideal binder for labour-based construction, if

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Table 1 Suitability for labour-based construction of bituminous surfacings on lowvolume roads

Minimum Junctionlocal Poor or

Cold Hot maintenance Steep surface turningSurface treatment emulsion bitumen1 capacity gradient drainage trucks

Priming Good2 Good

Sand seal Good Good No No No No

Slurry seal Good Not used 10 mm No Yes 10 mmlayer layer

Single Otta Good5 Fair3 Yes No Yes No

Double Otta Good5 Fair3 Yes Yes Yes Yes

Single Otta with sand seal Good5 Fair3 Yes No Yes No

Single surface dressing Good Good No No No No

Double surface dressing Good Good Yes Yes Yes Yes4

Pre-mix bitumen and gravel Good Not used Yes Yes Yes Yes

Penetration macadam Good Not used Yes Yes Yes Yes

1 A safe method of heating is essential.2 Invert emulsion only.3 Good if adequate compaction can be achieved.4 With third seal, fine aggregate is added to reduce damaging action on chippings.5 Emulsion must be HFMS-2s grade (minimum 200 Pen base bitumen).

equipment is available for the safe handling of hot binders, then they may beused if emulsions are not suitable. Selection of an appropriate bituminoussurfacing will depend on the materials to be used, the site characteristics suchas steep gradients and the equipment that is available for construction. A guideto the selection of the surface treatments is given in Table 1 and Figure 1.

2.1 Surface treatmentsSand sealThis seal consists of first a prime coat, a film of binder (cutback bitumen,emulsion) followed by graded sand (3-5 mm) which must then be compacted.

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Performance can be improved if a second seal is applied after 3 months. A lifeof 4-5 years can be expected. It is primarily a temporary surfacing, or forapplication on top of other seals. It is especially useful if good aggregate ishard to find, in deserts for example, and is suitable for labour-basedconstruction, especially where emulsions are used.

Figure 1 Basic selection of bituminous surfacings

Canbituminousbinder be

safely heated?

Choosebetween

Emulsion

MC3000cut-back

Sand SealSingle Surface DressingDouble Surface DressingSingle Otta SealDouble Otta Seal

Steepgradient orcrossfall?

Penetration MacadamPre-mixed Bitumen and Gravel

HFMS-2sgrade

emulsionavailable?

Single Otta SealDouble Otta Seal

Sand SealSlurry SealSingle Surface DressingDouble Surface DressingPre-mixed Bitumen and GravelPenetration Macadam

Steepgradient orcrossfall?

Double Surface DressingDouble Otta seal

No

No

Yes

Yes

Yes

Yes

No

No

4

Slurry sealSlurry seals are laid cold and are a mixture of fine aggregates, Portland cementfiller, binder emulsion and additional water. When freshly mixed they have athick creamy consistency and can be spread to a thickness of 5 to 10 mm. Thismethod of surfacing is not normally used for new construction because it ismore expensive than surface dressing and is not as durable as a properlydesigned and constructed surface dressing. On large-scale projects, slurrymixes are made and spread by purpose made machines. However, on lowvolume roads and on short sections, they can be suitable for labour-basedconstruction using portable concrete mixers.

Otta sealAn Otta seal consists of a layer of binder followed by a layer of aggregate thatis rolled into the binder using a pneumatic tyred roller or loaded trucks. It isdifferent to surface dressing in that a graded gravel or crushed aggregatecontaining all sizes, is used instead of single sized chippings. It depends for itssuccess on the binder being squeezed up through the aggregate by the actionof extensive rolling. Due to the fines in the aggregate, 2 to 3 days ofpneumatic-tyred compaction (rollers or traffic) are required to fully coat allthe particles. An Otta seal may be applied in a single or double layer.Evidence on the performance of these types of seal constructed byconventional plant methods has shown them satisfactory for over 12 years onroads carrying up to 500 vehicles per day. Otta seals have a tolerant andforgiving design and are well suited to labour-based construction methods.

Binder and aggregate design is by judgement and must be established throughtrials. Inadequate trials can give poor results and a loss of confidence in theconstruction technique. Normally a cut-back bitumen, MC3000 or 150/200penetration grade bitumen is used with either a fine or coarse aggregate coverdepending on the level of traffic. Hard grade binders such as 80/100 cannot beused, as it is too viscous. Ordinary grade emulsions also, should not be used inthe construction of Otta seals. However, emulsions with a base bitumenpenetration of 200 such as HFMS-2s grade can be used. A wide range ofaggregate sources and types can be used.

Surface dressingUntreated road surfaces that are to be surface dressed must first be primed.The surface dressing comprises a thin film of binder sprayed onto thepreviously primed surface and then covered with a layer of stone chippings.The thin film of binder acts as a waterproofing layer preventing the entry ofsurface water into the road structure. The stone chippings protect this film ofbinder from damage by vehicle tyres, and form a durable, skid-resistant and

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dust-free wearing surface. It can provide an effective and economicalrunning surface for newly constructed road pavements. Roads carrying up to1000 vehicles/lane/day are successfully surfaced with multiple surfacedressings, but typically, the process is reserved for surfacing more lightlytrafficked roads, carrying up to 500 vehicles/lane/day. Double surfacedressings are usually used to seal an unpaved surface with single surfacedressings normally being used as a maintenance treatment for existingbituminous sealed roads. A correctly designed and constructed surfacedressing should last at least 5 years and longer on very lightly traffickedroads, before resealing with another surface dressing becomes necessary.Surface dressings can be constructed in a number of ways to suit siteconditions, the most common being a single or double seal.

Surface dressings are less tolerant of labour-based methods compared to Ottaseals, as they require accurate rates of spread of both binder and surfacingaggregate. However, they can be successful if hand spraying of the binder isdone carefully by suitably trained operators. With this in mind and consideringthe safety to the workforce and environmental aspects, emulsions are bestsuited to labour based methods.

The single and double surface dressing methods described in this manual arebased on a full design method summarised in Appendix B.

Pre-mixed bitumen and gravelThis type of surfacing is made by mixing gravel with a stable slow breakingemulsion either by hand or in a small drum mixer such as a portable cementmixer. The aggregate gravel specification is the same as for an Otta seal. Aftermixing, the material is spread on a primed roadbase and rolled. The surfacingis comparable to an Otta seal after some months of trafficking.

Penetration macadamAfter trafficking, Penetration Macadam is effectively similar to asphalt. It isconstructed to be at least 50 mm thick and is very robust compared to thin sealcoats. This type of surfacing is, therefore, likely to be the best solution forsites where traffic and road geometry is severe. The cost of this surfacing willbe relatively high because screened crushed rock aggregate is requiredtogether with a high rate of application of binder. However, cold emulsion issuitable for this process and this makes it one of the surfacings best suited tolabour-based construction.

Crushed aggregate is normally used because this material helps to generate astable interlocking layer after it has been compacted. A heavy (8 Tonne) roller

6

is needed and the road base must be strong enough to resist the aggregatepunching in. Uncrushed gravel materials can be used if the aggregate particleshave some surface texture and traffic is light. Suitable aggregates can also beproduced by hand-knapping if necessary.

3 Materials for bituminous surfacings

Safety considerations must be taken into account when selecting bitumen forlabour-based work. The application of hot binders require the use of purposemade towable heater tanks with a built in spray bar or an attached hand lance.

3.1 Cut-back bitumensThese binders must be heated before they can be applied. Applicationtemperatures are lower for bitumens cut-back with more solvent (kerosenetype material) but the risk of fire increases. Typical spraying temperatures forcut-back bitumens for hand lance spraying are given in Table 2.

3.2 Bitumen emulsionsBitumen emulsion is commercially available in different types and grades.Inverted emulsions (i.e. water suspended in bitumen) are available and areused as primes whilst anionic and cationic emulsions are suitable for differenttypes of aggregates and uses.

Emulsions containing less than 70 per cent bitumen can be sprayed and mixedat ambient temperatures. Emulsions that contain greater than 70 per centbitumen require heating to approximately 70ºC.

Anionic emulsions can give poor adhesion with acidic rocks (such as graniteand quartzite) but good adhesion with basic rocks (such as basalt) and withlimestone. Cationic emulsions are suitable for use with both rock types. The

Table 2 Spraying temperatures for cut-back bitumens

Bitumen type Slotted jets

Cutback grades MinºC MaxºC

MC30 (Prime) 40 50MC70 (Prime) 55 70MC3000 120 130

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addition of small percentages of fresh hydrated lime, or sometimes Portlandcement, to the aggregate will improve adhesion of anionic emulsion to acidicrocks.

There are three grades of anionic and cationic emulsions; Rapid, Medium, orSlow setting and normally contain between 40 and 70 per cent bitumen, 65 percent being the best for most labour-based work.

The main uses of bitumen emulsions are given in Table 3.

Table 3 Uses of common bitumen emulsions

Grade of emulsion Appropriate uses

Rapid setting RS Sand seals.Surface dressing.Penetration macadam.

Medium setting MS Pre-mixed bitumen and gravel (coarse grading).

Slow setting SS Otta seal1.Pre-mixed bitumen and gravel (fine grading).Slurry seal.

1 Minimum 200 penetration grade based bitumen (e.g. HFMS-2s)

Some emulsions such as slow setting grades can be diluted with water ifnecessary but a test on a small quantity of emulsion and water should becarried out to confirm that the quality of the water is satisfactory. If thebitumen coagulates then a new source of water must be found.

3.3 AggregatesClean crushed rock that can be produced by handknapping and screeningshould be used for penetration macadam.

Clean single sized crushed gravel or rock should be used for surface dressings.The chippings that are available to the contractor may be of varying quality,but generally, they will be able to be classified into three types. They are:

� Rounded Worn round by the action of water and friction.

� Angular Having easily seen edges and roughly cubical in shape.

� Flaky Thickness less than approximately half the length or width.

8

Single sized chippings should be produced by screening. A simple screeningframe is shown in use in Plate 1.

Clean gravel with little fine material or crushed rock can be used for Otta sealsand pre-mixed bitumen and gravel. Oversize aggregate greater than 16 mmshould be screened out.

4 Tools and equipment

Labour-based construction methods require an adequate number of hand toolsand equipment to successfully carry out the task. Most are relativelyinexpensive, either already in the possession of the local labour force or areeasily obtained. In addition, small mechanised plant that a contractor mayhave should be employed whenever possible. The plant will provide the meansto more accurately meet construction requirements and speed up the work.The tools and equipment that are thought essential for various types of labour-based work are listed below. The numbers of each item required will dependon the nature of the surface treatment and the size of the construction project.

� Shovels.

� Pickaxes.

� Hoes.

� Brooms.

Plate 1 Screening frame

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� Rakes.

� Buckets.

� Watering cans.

� Measuring containers of known volume.

� Steel measuring tape (50 metre).

� String.

� Hand tampers or rammers.

� Steel pegs or nails.

� Balance or scales, 20 kg minimum capacity.

� Large clock.

Particular plant required for labour-based construction can include thosedescribed in Plates 2 - 7.

To discharge the bituminous binder (usually emulsions) into smallermeasuring containers an easily removable gate valve/tap must be used. Thiswill help to keep a clean operation without undue wastage. The drum must berolled up a ramp onto a stand that can be made locally. The stand must be highenough to clear the containers beneath.

Plate 2 Stand for drum of bituminous binder.(Photograph courtesy of South African National Roads Agency)

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Half of a 210 litre drum with the top and bottom open and with metal handlesattached is light, economical and can be made locally. It is used for placingheaps of aggregate along the length of the road surface to be treated.

Although small quantities may be mixed by hand, a portable concrete mixer ofapproximately 200 litres capacity can be used to efficiently mix aggregate andemulsions to produce slurries and premix gravels.

Plate 4 Portable concrete mixer.(Photograph courtesy of South African National Roads Agency)

Plate 3 Open top and bottom drum.(Photograph courtesy of South African National Roads Agency)

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Compaction of surfaces can be achieved with the use of small pedestrianrollers.

Plate 5 Pedestrian roller.(Photograph courtesy of South African National Roads Agency)

Plate 6 Lorry wheel compaction

Compaction of surfacings can also be carried out using a heavily loaded lorry.This method is especially suitable for the rolling of Otta seals.

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The pump and lance are fitted to a four-wheeled trolley that carries a drum ofbituminous binder, usually emulsion or prime that can be sprayed at ambienttemperature.

4.1 Spraying by hand lanceA hand lance is fitted with a motor driven pump that operates at constantspeed. Adjusting the setting on the pump by-pass system controls the pressureat two hand lance jets.

During spraying the lance must be held at a height that gives a 50 per centoverlap of the spray from each jet as shown in Figure 2. It is then possible totime a pass across a lane width, perpendicular to the centre-line of the road, toprovide the correct application rate of bitumen.

Plate 7 Motor powered pump and hand-lance sprayer

Figure 2 Overlap of spray from hand lance sprayer

Spraybar

Spray bar held at a height

that gives 50 per cent overlap

of the spray from each jet

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The bituminous binder should be applied as the operator and trolley movebackwards along the road. The spray pattern on one pass results in one third ofthe area receiving half the output of the trailing jet, one third receiving half theoutput of both jets and the final third receiving half the output of the leadingjet. The first pass should be made with the trailing half spray being made onloose sand (a paper strip could be used) and the subsequent passes overlappedto ensure that all of the road surface receives half the output from each jet.This is illustrated in Figure 3.

Figure 3 Spray coverage of the road surface

At the end of each pass, the lance has to be pulled back sharply to the newspraying position to avoid applying too much binder at the centre-line androad edge.

Large cut-off boards or screens can be used to ensure that a clean cut off in thebitumen is produced along the centre-line of the road and at the road edge.However, the nature of the spray produced by the lance and the method in

½ spray from trailing jet

sprayed on sand or paper

Spray from both jets

½ spray from the leading jet

½ spray from trailing jet on 1st pass

sprayed on sand or paper

Spray from both jets on 1st pass

½ spray from leading jet on 1st pass

½ spray from trailing jet on 2nd pass

Spray from both jets on 2nd pass

½ spray from leading jet on 2st pass

1st pass

1st pass

2nd pass

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which it is used must be considered if cut-off boards are used. The skin andeyes of people holding the boards and all other operatives should be protectedfrom contact with sprayed binder and from any fumes that may be produced.Rubber gloves, safety glasses and facemasks are considered suitable for thispurpose.

It is important that operators of the hand sprayers are fully trained beforehandin its use. The training and practice in the use of hand sprayers should becarried out on ground away from the road to be treated. A good way to begintraining is to use water as the sprayed liquid. In this way there will be nodamage to the surrounding environment.

5 Health and safety

All of the bituminous surfacings described in this manual involve the use ofbituminous binders during construction. Depending on the particular surfacingor the availability of binder, they may be hot cut-back bitumens or bituminousemulsions that are applied cold.

Emulsions that can be sprayed at ambient temperature or need only slightheating in a towable heater tank are most suitable for labour-based methods.There is no evidence to suggest serious health hazards are associated with theuse of bitumen emulsions. However, repeated or prolonged skin contactshould be avoided to minimise the chance of skin sensitisation. Contact withskin can be avoided by the wearing of protective clothing, rubber gloves andboots. At the end of the working day, the workforce should thoroughly washexposed skin with soap and water. Solvents such as kerosene should not beused as they in themselves may cause skin irritation. The wearing of goggleswill protect eyes but where eyes are accidentally splashed, they should beflushed with large amounts of water and medical help sought.

The use of hot bitumen presents hazards for the labour force and theavailability of heating fuel may be limited or its use environmentallyundesirable. Generally, heating of bitumen should be carried out in a purposemade towable heater tank typically fitted with a spray bar or hand lance forlabour-based work. A hazard is the risk of burns to exposed skin. Burns shouldbe immediately drenched with cold water for at least 10 minutes or until cool.No attempt should be made to remove any binder that has stuck to the skin.The binder will gradually lift from the skin by itself after a few days. Tominimise the risk of burns, protective heat resistant gloves and footwearshould be worn. The heating of bitumens can generate large volumes of fumesthat must not be inhaled.

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It is essential for the safety and health of the workforce that good workingpractices are observed at all times. The operators of equipment such asconcrete mixers and hand sprayers must be fully trained and familiar withtheir use.

6 Project organisation

6.1 PlanningIt is important that preparation of the surface to be treated and application ofthe materials used in the construction of all the surfacings be carried out in anorganised way to ensure the correct stages take place at the right time.

Before any bituminous surfacing is constructed, the existing unpaved surfacedroad must be prepared if necessary by reshaping, compacting and providingdrainage.

Some basic steps and decisions must be made. A list should be madeitemising:

� Number of workers needed.

� Tools and equipment needed.

� Type and quantity of materials needed.

� Transport of the workers, materials and equipment to the road site.

During construction of the bituminous surfacings, methods of measuringaggregate and bitumen quantities will be required. This can be done usingrelatively inexpensive containers. Examples that may be used are:

� Buckets (10 litre).

� Watering cans (10 litre).

� Empty drink (soft drink and water) bottles (2 litre and 1 litre).

� Empty fuel cans (25 litre).

� Empty paint containers (5 litre and 2½ litre).

� Any empty container where the volume is known or can be measured and isbetween 2 and 25 litres.

Special use can be made of an empty 210-litre drum. It should be cut in half withthe bottom also removed. This will make a cylinder open at the top and bottom.Set amounts of sand, chippings or gravel can then be transferred from

16

wheelbarrows into the drum until it is full. Lifting away the drum at points alongthe road then places the material where it is needed to be spread from. See Plate 3.

Immediately prior to any construction, the surface of the road must be sweptclear of loose material and mud. Repairs must be made to potholes or anydepressions that may have formed since the reshaping of the road. It isrecommended that a light spray of water be applied prior to priming of thesurface the day before the construction of the surfacing.

Before construction can take place the spread rate of aggregates must beestablished. Typical spread rates are given in Table 4. Sufficient aggregatewill need to be prepared and stockpiled along the road.

The sealing operation must be carried out in dry weather and must not begin ifthere is a threat of rain or if a strong wind is blowing. Construction should beginwith the setting out of the area that can be treated in one day. Stockpiles ofsufficient chippings or aggregate should be placed along the roadside, at intervalsshown in Table 5, ready to be spread by hand after application of the binder.

The application of primer to the existing gravel surface and the subsequentapplication of the bituminous binder can be carried out either by a handpumped sprayer or watering cans. The area of the surface that can be coveredby one watering can must first be marked into smaller areas (for example 1metre wide). This will help in the even distribution of the binder. Morereliable and accurate spray rates can be achieved using the hand sprayermethod but the rate of delivery of the sprayer must be known. This can be

Table 4 Sand / aggregate / chipping spread rates and coverage

Appproximatearea half drum

Treatment Spread rate will cover (m2)

Sand seal 13 - 19 kg/m2 17.5

Otta seal 0.013 - 0.016 m3/m2 7.5

Single surface dressing 12.51 kg/m2 11.51

Double surface dressing 1st layer 12.51 kg/m2 11.51

Double surface dressing 2nd layer 4.02 kg/m2 352

1 14 mm chippings.2 6 mm chippings.

17

determined easily by timing how long it takes to fill a container of knownvolume. It is important that operators of the hand sprayers are fully trainedbeforehand in its use. The rates of delivery calculated using 10 and 5 litrecontainers are shown in Appendix C.

It is essential that sufficient time is given well before any construction takesplace to ensuring hand lance operatives are well trained in the use of theequipment and can deliver the correct rates of spray.

6.2 WorkforceThe size and makeup of the workforce will vary with the size of the projectundertaken. A supervisor with some experience and practical knowledge ofroad construction should be appointed to be in charge of 3 or 4 teams. Thesupervisor must be responsible for taking charge of everyday organisationaland technical problems, be competent in the methods of construction to beused and have the authority to give instructions on-site to the team leaders andworkforce. For most construction work, a basic team of 20 - 25 labourersunder the direction of one team leader can be employed. The team leadershould be experienced and have the confidence and respect of his team. Teamleaders and the workforce need not have had any formal training in roadconstruction. If the workforce is inexperienced then training must be receivedduring the course of construction through practical demonstrations andinstructions from the supervisor.

Table 5 Approximate interval between aggregate placement (to the nearest 0.5 metre)

Width of area to be treated (metres)

2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0

Treatment Approximate aggregate spacing (metres)

Sand seal 9.0 8.0 7.0 7.0 6.0 6.0 5.5 5.0 5.0 4.5 4.5

Otta seal 3.5 3.5 3.0 2.5 2.5 2.5 2.5 2.0 2.0 2.0 2.0

Single surface dressing1 6.0 5.0 5.0 4.5 4.0 4.0 3.5 3.5 3.0 3.0 3.0

Double surface dressing 1st layer1 6.0 5.0 5.0 4.5 4.0 4.0 3.5 3.5 3.0 3.0 3.0

Double surface dressing 2nd layer2 17.5 16.0 15.0 13.5 12.5 11.5 11.0 10.0 9.5 9.0 9.0

1 14 mm chippings.2 6 mm chippings.

18

7 Preparation of existing road surface

The performance and success of any bituminous surfacing will depend on thecondition and strength of the existing surface that it is to be constructed uponand the provision of drainage. There will normally be some need to preparethe road surface. How this is carried out and to what specifications will bedependent on local circumstances but a summary of what should beconsidered and actions to take is shown in Figure 4.

Figure 4 Surface preparation plan

One of the most important aspects of the design of a road is the provisionmade for protecting the road from surface water or ground water. The roadsurface must be constructed so that it drains rainwater away quickly todrainage ditches. The formation of the road must be raised above the level ofthe local water table to prevent it being soaked by ground water.

Is there any gravel

on the surface?

No

Yes

Does the gravel cover

all of the surface?

No

1. Reshape surface 2. Compact by rolling 3. Improve drainage if needed

Yes

1. Reshape existing road 2. Compact by rolling3. Add gravel4. Compact by rolling

1. Add more gravel 2. Scarify 3. Compact by rolling

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A road that is flat or dished will collect water and this will cause the surface todeteriorate rapidly. Therefore, the road should be shaped so that the surfacefalls away either side of the centre line of the road (crossfall). This can bedone by loosening the existing surface, adding and mixing in more material asnecessary, returning material from the road edges towards the centre of theroad, and recompacting as directed in Table 6.

1 Mark the centre line ofthe road with pegs every10 metres.

2 Set out the pegs for theroad edges and guttersusing tape measure andcamber board.

3 Material may be dugfrom a backslope orbeyond the gutter.

4 Compact the fill materialto the required camberusing a motorisedpedestrian roller or hand,animal or tractor drawnroller. See Plate 9.

Table 6 Reshaping of road surface

Procedure

Passes by roller

1st 3rd 5th 6th 4th 2nd

20

The crossfall on bituminous surfaced roads should normally be between 1 in40 (2.5%) and 1 in 33 (3%). When bituminous emulsion is to be used, theshallower slope should be used. The final shape of the road surface ready forbituminous surfacing is shown in Figure 5. It should be checked using asimple camber board, such as that illustrated in Plate 8 and in Figure 6. Use ofthe camber board is illustrated in Figure 7. It should be placed on its edgeacross the road with its narrower end pointing towards the centre line. If thelevel bubble is central, then the camber is correct. Checks should be made atapproximately 10 metre intervals along the road and if the camber is too steepor too flat, then the road must be graded again.

Figure 5 The road shaped ready for bituminous treatment

Plate 8 Camber board

2.5% 2.5%

RoadwayBac

kslope

Ditc

h

Slope

21

155mm

1800 mm

155 mm200 mm

(20 mm plywood) Level bubble

Level bubble

Figure 6 2.5% camber board

Figure 7 Use of camber board

Plate 9 Hand drawn roller

22

7.1 Methods of preparationThe principal operations in preparing unpaved roads before the construction ofa bituminous surface are grading, with the addition of gravel and compactionof the surface by some means of rolling.

7.1.1 GradingGrading is used to reshape the road to the correct camber or crossfall and toprovide a surface suitable to apply a bituminous layer. Light grading is a lighttrimming of the surface of the road. In the dry season, loose material should bebladed towards the edge of the road. In the wet season, material should begraded towards the centre of the road. Motor graders may carry out lightgrading, but a more cost-effective technique is to use tractor-towed gradersthat are capable of sufficient outputs and standard of work.

Heavy grading consists of scarifying as shown in Plates 10 and 11 and cuttingto the bottom of deformations and then reshaping the surface. It usuallyrequires the use of a 135 horse power motor grader but, in some cases, atractor-towed grader could also be utilised. When possible, it should be carriedout at the end of the wet season when the moisture content of the surfacingmaterial is still high enough to achieve recompaction. This is particularlyimportant when heavy grading is needed to remove ruts and potholes.Scarifying to the depth required to remove these will result in the productionof a considerable depth of loose materials and, in the dry season, this cannotbe recompacted unless water is added.

Grader operationThe quality of workmanship in preparing the road surface for bituminoustreatments depends largely on the skill and judgement of the individual graderoperator. Careless operation can cause extensive damage to a road, forexample by flattening the crown so that rainwater is not discharged, by cuttingtoo deeply in dry weather or by blading plastic material from side drains ontothe carriageway.

For heavy grading, the grader works on one side of the road at a time, ifpossible, and works in passes of about 200 metres in length. On straightstretches of road, the operator should aim to develop a crown on the road. Thesurface should be cambered to fall away from the crown with a slope of 2.5-3per cent. The shape of the road must be maintained across culverts but, onsharp bends, the surface must be super elevated and must be flat from shoulderto shoulder with the outer shoulder higher. Any crown on a bend can be verydangerous to traffic. On the transition from bends in the road to straight

23

sections, the camber on the outside lane should be gradually reduced until thenormal cross-section shape is obtained again (see Figure 8).

For heavy grading, it is important to cut to the bottom of surface defects and,if the road surface is hard, the grader’s rippers should be used to loosen thematerial. The grader should start from the edge of the road and work towardsthe centre. The first and second passes cut to the bottom of the surface irregu-larity and deposit a windrow just beyond the centre line. The windrow is thenspread back across the road depositing all the material on the carriageway togive the correct camber. The material may need to be sprayed again withwater during this operation. After the camber has been checked, the other side

Plate 10 Tractor towed scarification

Plate 11 Scarification

24

Figure 8 Camber on approach to bends

of the carriageway is graded in a similar way to complete the work and leave asmooth even surface. This is illustrated in Figure 9.

It is important that the grader does not make a final pass down the centre ofthe road with the blade horizontal. This flattens the centre of the road andcauses water to pond.

7.1.2 RegravellingSome roads that are to be treated with a bituminous surfacing may be damagedto the extent where regravelling to a compacted layer depth of 100 mm isrequired. Before regravelling work is carried out, it is important to make anynecessary repairs or improvements to the drainage system of the roadincluding the clearance of blocked culverts.

Quality of gravelIn practice, what gravel is used will depend largely on what is available, and itmay be necessary to use lower-grade material than is commonly specified.The fines of the gravel should ideally be non-plastic but should normally notexceed a Plasticity Index (PI) of 6. However in arid and semi-arid areas,

25

material with PI of up to 30 can be used. The facilities of a materialslaboratory to measure such variables as plasticity will rarely be available andthe following methods may be used to assess the gravel material.

Crumble a dry sample of the gravel material in the hands. About half byvolume of the particles should be larger than 2 mm in diameter. Attempt tocrumble the large particles in the hand by lightly tapping with a hammer. Ifthe lumps disintegrate completely into sand size particles, the material will notbe suitable for gravelling.

The ability of the gravel material to bind together is dependent on the presenceof cohesive fine material. These can be checked for by moulding a dampsample of the gravel into a ball. If cohesive fines are present, the material willstick together when gently placed on a flat surface.

Good gravel should have a mixture of stones, sand and clay roughly in thefollowing proportions:

1

2

3

4

5

Figure 9 Grading

26

Stone (> 2 mm) 50 per cent

Sand 40 per cent

Clay 10 per cent

Placing a sample of material in a glass jar and adding some water can check theproportions. The jar and contents should be shaken vigorously and left to standfor some hours. The approximate quantities of each size of particle can be seenas layers in the sample with the finer material being of a different colour.

7.1.3 CompactionCompaction rollers must follow up closely behind the grader but must onlywork on sections where grading has been completed to avoid interference withthe grading operation. Rolling should start at the edge of the road and worktowards the middle and be repeated by a number of passes until full compactionhas been achieved. The number of passes required will depend on the type andweight of the roller used. Table 7 gives a guide to the number of passes to bemade to adequately compact a 100 mm gravel layer with typical kinds of rollerused in labour-based construction. Providing the work is carried out in the wetseason, little watering of the road will be necessary before rolling. Otherwise,water should be added as required, during the rolling operation.

Table 7 Roller compaction and number of passes required

Operating WidthNumber speed compacted

Roller type of passes (km/h) (m)

Smooth wheeled 8 tonne tandem 8 2.5 1.3

Pedestrian vibratory 600 kg 161 5 0.6

Vibratory plate compactor 700 kg 6 1 0.7

Manual roller 700kg 12 – 0.9

1 Compacted in two lifts of 50mm.

27

28

8 Priming

Description of treatmentWhere a bituminous surfacing is to be applied to an untreated road surface it isimportant that the surface should be dry, clean and as dust-free as possible. Aprime coat of bitumen ensures that these conditions are met.

Priming helps maintain adhesion between the roadbase and the bituminoussurfacing and seals surface pores in the roadbase. It helps to strengthen theroadbase near its surface and if the surfacing construction is delayed itprovides the roadbase with a temporary protection against rainfall and lighttraffic until the surfacing can be laid. The surface should be lightly sprayedwith water before applying the prime coat as this helps to suppress dust andallows the primer to spread more easily over the surface and to penetrate theroadbase. Cutback bitumens such as MC30 that need no heating are applied ata typical application rate of 1.0 l/m2. A good alternative prime to apply is aninvert emulsion that can be applied with no heating. The typical applicationspray rate is 1.2 l/m2.

The depth of penetration of the prime should be 3-10 mm and the quantitysprayed should be such that the surface is dry within a few hours but normallya prime is applied 24 hours before the construction of a surface treatment.

Bituminous binder Spray ratesMC30 cut-back 1.0 l/m2

Invert emulsion 1.2 l/m2

Equipment and tools

� Measuring tape of minimum 10 metre length.

� Ball of string.

� Brooms.

� Cut off boards 2m × 1m.

� Clock or watch.

� Motor powered pump and hand lance sprayer.

Materials

� Water.

� MC30 cut-back bitumen or invert emulsion.

29

PRIMING

Preparation Notes

1 Priming must be carried out 24 hoursbefore the construction of otherbituminous surface treatments.

2 Sweep the roadbase from the centre Remove all loose material such as largeof the road to the road edges. stones and vegetation.

3 Measure out the area of the road to Mark out the area with string.be primed into sections.

4 Lightly spray water on to the roadbase This may be carried out using watering canssurface. that deliver a fine spray.

Construction Notes

1 Test the hand lance sprayer is working Test on waste ground.correctly.

2 Begin spraying the primer. Spraying begins at the signal of the personkeeping time.

3 The hand lance operative must spray The timekeeper must shout out the timeeach marked section in the prearranged elapsed in seconds to guide the hand lanceset time to give the correct spray rate. operatives progress.

4 Move the cut off boards positioned at The boards are held vertically to preventthe edges of the road as the hand lance overspray onto surface areas outside thoseoperative moves down the road. areas being primed. Two people to each cut

off board.

5 Continue until all of the roadbase hasbeen primed.

30

9 Sand seal

Description of treatmentA bituminous binder and a graded sand are applied to a primed base course toseal the surface as a light wearing course. Single sand seals are not verydurable. Application of a second seal after 3 months should give a life of 4-5years. They may also be applied as a final layer on other types of seals.

Sand seals are suitable for labour-based construction on roads carrying up to100 vpd where natural sand is plentiful. Cationic emulsion or hot bitumen issuitable for these seals. The design is based on experience of the performanceof materials and climate effects in the particular location.

Bituminous binder Spray ratesMC3000 cut-back bitumen 1.4 l/m2 Best applied with

tractor towedheating tank withspray bar or handlance.

Emulsion, 60% cationic 1.6 l/m2

Sand Spread rate13 - 19 kg/m2

Equipment and tools

� Measuring tape of minimum 10metre length.

� Ball of string.

� Shovels.

� Rakes.

� Brooms.

Materials

� Water.

� MC30 cut-back bitumen or invertemulsion for prime.

� Hand sprayer or watering cansfor unheated emulsions.

� Tamping tool.

� Squeegees.

� Pedestrian roller or tractor ortruck.

� Cut-back bitumen oremulsion.

� Screened river sand orcrusher dust (no materialgreater than 6.3 mm).

31

SAND SEAL

Preparation Notes

1 Broom and roll the surface.

2 Water the surface to be sand sealed.

3 Continue 1 and 2 until the surface is verysmooth and well compacted.

4 Prime the surface. Twenty four hours before sand sealconstruction.

Construction Notes

1 Sweep the base clear of loose material. Clay particles, animal droppings.

2 Apply the bituminous binder at the correct Spray rate, see page 30.spray rate.

3 Apply sand to the binder immediately Spread rate, see page 30.after spraying.

If the binder used is emulsion, wait untilthe emulsion has started to break (changingfrom brown to black in colour) beforeapplying sand.

4 Roll the treated surface with a pedestrianroller or lightly loaded truck.

5 Sweep loose sand back into the wheelpaths. For one or two weeks, continue this processfrom time to time.

6 A second seal may be constructed. Allow 12 weeks of trafficking on the firstseal.

7 Repeat 3 - 6 of the above method of Sweep clear any loose sand remaining onconstruction. the first seal before applying binder.

32

10 Slurry seal

Description of treatmentA mixture of fine aggregates, cement filler, binder emulsion and additionalwater. This type of surfacing is relatively expensive and works best when laidon an existing bituminous surfacing or a crushed stone roadbase. However, itcan be used on low volume roads. As a first surfacing, it should be applied intwo layers each being of 5-10 mm thick.

Material quantitiesThe quantities of the material needed for one mix are calculated from knowingthe size or volume of the mixer. The calculations are as follows:

Crusher dust = Mixer volume × 0.69 litres

Emulsion = Mixer volume × 0.17 litres

Water = Mixer volume × 0.11 litres

Cement = Mixer volume × 0.02 litres

Equipment and tools

� Concrete mixer.

� Wheel barrows.

� Measuring tape of minimum10 metre length.

� Ball of string.

� Shovels.

� Rakes.

� Brooms.

� Buckets.

� Containers 25, 2, 1 litres.

� Rope.

� 10 mm thick metal rails or woodenbatons.

� Spreader rail.

� Wide rubber squeegees.

� Rubber boots.

� Diesel/petrol/oil for mixer.

� Clean water.

33

SLURRY SEAL

General Notes

1 Prime the roadbase surface. Twenty four hours before slurry sealconstruction is to begin.

2 The area where the concrete mixer is Dirt and mud must not be carried by theoperating must be have a good surface wheelbarrows onto the surface to be treated.and be kept clean.

3 Crusher dust must be dumped close to Mid-point of the section of road to bethe mixing site. treated to the side of the road.

4 The concrete mixer must be checked for Concrete mixer operator is responsible.oil and fuel.

5 At the end of the work day, the mixer Concrete mixer operator is responsible.must be cleaned out with water.

6 The mixing and road works site must Wheelbarrow operators responsible.be kept clean of slurry spillage orcontaminants such as mud.

Mixing Notes

1 Start the mixer and set turning. The volume of the mixer must be known formaterial quantities.Material quantities, See page 32.

2 Use measuring containers to add the Supervisor of mixing operation iscorrect amount of aggregate. responsible.

3 Slowly add the cement to the aggregate. Make sure the aggregate and cement arewell mixed.

4 Add a small amount of water.

5 Slowly add the emulsion. A little at a time to prevent splashing.

6 Carefully add the rest of the water. 2.5 litres at a time and allow time forcomplete mixing.

Inspect the mixture after each addition ofwater to decide if the full amount of water isrequired to get the correct creamyappearance.

Continued ....

34

SLURRY SEAL (Continued)

Spreading and placing Notes

1 The surface of the road should be Sweep clear.checked for loose materials.

2 Mark the lines for the metal rails with The distance between the rails should be soa string line and place the rails. the minimum amount of discharge and

spreading is needed.

The rails gauge the depth of the wet slurry.10 mm depth rails ensure a final minimumdepth of 6 mm.

3 Lightly sprinkle water over the area No slurry should be placed on a dry surface.to be treated. Ensure no free standing water on surface.

4 Wheelbarrows are needed to transportslurry from the concrete mixer to the road.

5 Discharge the slurry mixture into The concrete mixer operator is in charge ofwheelbarrows in half barrow loads. the transfer of slurry from mixer to

wheebarrow. The operator should ensure themixture falls into the bowl of the barrowwithout any wastage.

6 Transfer the half barrow loads of slurry During this operation the shovels must bebetween the rails or batons using shovels. dipped into water and wiped with a wet cloth.

7 Spread the slurry over the surface betweenthe rails with rubber squeegees.

8 Ensure consistent depth. Two operators to work a spreader rail backand forth at right angles across the rails.

9 The spreader rail and all hand tools Water for cleaning may be kept in a halfshould be kept clean. drum near the place of work by transporting

it in a barrow.

10 Wipe out empty barrows with a wet Wheelbarrow operators responsible.cloth to remove any slurry remainingstuck to the bottom of the barrow.

No traffic is to be allowed on the surfaceuntil the emulsion has broken and set.

Stable grade anionic emulsion can take2 to 3 hours for breaking to happen.

11 Apply a second layer. The procedure follows that for the first layer.The first layer must be dry and have beenopen to traffic for 24 hours.

35

36

11 Single surface dressing

Description of treatmentOn a gravel road, one layer of bituminous binder is sprayed onto the roadsurface followed by a layer of chippings and finished with a sand seal.

A surface dressing can be successfully constructed using either hot cut-backbitumen such as MC 3000 or a rapid breaking cationic emulsion such as K1-60that requires no heating. The physical characteristics of the site and the abilityto safely heat binder will determine which is used. Generally, on road surfaceswith no steep crossfalls or gradients, it is advisable to use an emulsion as thebinder.

Bituminous binder Spray rateMC3000 cut-back See Tables 8 - 10

Emulsion, 60% cationic See Tables 11 - 13

Chipping spread rate See Tables 14

The full surface dressing design for these and other conditions can be found inAppendix B.

Equipment and tools


� Vernier gauge.

� String.

� Shovels.

� Rakes.

� Brooms.

Materials

� Water.

� MC30 cut-back bitumen or invertemulsion prime.

� Hand sprayer or watering cansfor emulsions only.

� Safe method for the heating ofMC3000.

� Buckets.

� Tamping tool.


� MC3000 cut-back bitumen orbituminous emulsion.

� Nominal single size stonechippings.

37

Table 8 14 mm chippings, MC3000 binder spray rates

Binder spray rate (litres per square metre)

Climate

Hot and wet Hot and dry

Type of chippings2 Type of chippings2

ALD1 mm Rounded Angular Flaky Rounded Angular Flaky

8 1.3 1.2 1.2 1.2 1.2 1.18.1 1.3 1.2 1.2 1.2 1.2 1.18.2 1.3 1.3 1.2 1.3 1.2 1.18.3 1.3 1.3 1.2 1.3 1.2 1.18.4 1.3 1.3 1.2 1.3 1.2 1.18.5 1.3 1.3 1.2 1.3 1.2 1.18.6 1.3 1.3 1.2 1.3 1.2 1.18.7 1.3 1.3 1.2 1.3 1.2 1.18.8 1.3 1.3 1.2 1.3 1.2 1.28.9 1.4 1.3 1.2 1.3 1.2 1.29 1.4 1.3 1.2 1.3 1.2 1.29.1 1.4 1.3 1.2 1.3 1.2 1.29.2 1.4 1.3 1.2 1.3 1.2 1.29.3 1.4 1.3 1.2 1.3 1.2 1.29.4 1.4 1.3 1.2 1.3 1.2 1.29.5 1.4 1.3 1.2 1.3 1.2 1.29.6 1.4 1.3 1.3 1.3 1.3 1.29.7 1.4 1.3 1.3 1.3 1.3 1.29.8 1.4 1.3 1.3 1.3 1.3 1.29.9 1.4 1.3 1.3 1.3 1.3 1.210 1.4 1.3 1.3 1.3 1.3 1.2

1 The Average Least Dimension (ALD) is a measure of the average size of chippings and howflaky they are. ALD is obtained by taking a sample of 200 chippings and measuring the leastdimension of each chipping with a vernier gauge and calculating the average value.

2 See Section 3.3, page 7.

38



Climate


Type of chippings Type of chippings

ALD mm Rounded Angular Flaky Rounded Angular Flaky

5 1.2 1.1 1.0 1.1 1.0 1.05.1 1.2 1.1 1.0 1.1 1.0 1.05.2 1.2 1.1 1.0 1.1 1.0 1.05.3 1.2 1.1 1.1 1.1 1.1 1.05.4 1.2 1.1 1.1 1.1 1.1 1.05.5 1.2 1.1 1.1 1.1 1.1 1.05.6 1.2 1.1 1.1 1.1 1.1 1.05.7 1.2 1.1 1.1 1.1 1.1 1.05.8 1.2 1.1 1.1 1.1 1.1 1.05.9 1.2 1.1 1.1 1.1 1.1 1.06 1.2 1.1 1.1 1.1 1.1 1.06.1 1.2 1.2 1.1 1.2 1.1 1.06.2 1.2 1.2 1.1 1.2 1.1 1.06.3 1.2 1.2 1.1 1.2 1.1 1.06.4 1.2 1.2 1.1 1.2 1.1 1.06.5 1.2 1.2 1.1 1.2 1.1 1.06.6 1.2 1.2 1.1 1.2 1.1 1.16.7 1.2 1.2 1.1 1.2 1.1 1.16.8 1.2 1.2 1.1 1.2 1.1 1.16.9 1.3 1.2 1.1 1.2 1.1 1.17 1.3 1.2 1.1 1.2 1.1 1.1

39



Climate




2 1.0 1.0 0.9 1.0 0.9 0.92.1 1.0 1.0 0.9 1.0 0.9 0.92.2 1.0 1.0 0.9 1.0 0.9 0.92.3 1.0 1.0 0.9 1.0 0.9 0.92.4 1.0 1.0 0.9 1.0 0.9 0.92.5 1.0 1.0 0.9 1.0 0.9 0.92.6 1.0 1.0 0.9 1.0 0.9 0.92.7 1.0 1.0 0.9 1.0 0.9 0.92.8 1.0 1.0 0.9 1.0 0.9 0.92.9 1.0 1.0 0.9 1.0 0.9 0.93 1.1 1.0 0.9 1.0 0.9 0.93.1 1.1 1.0 1.0 1.0 1.0 0.93.2 1.1 1.0 1.0 1.0 1.0 0.93.3 1.1 1.0 1.0 1.0 1.0 0.93.4 1.1 1.0 1.0 1.0 1.0 0.93.5 1.1 1.0 1.0 1.0 1.0 0.93.6 1.1 1.0 1.0 1.0 1.0 0.93.7 1.1 1.0 1.0 1.0 1.0 0.93.8 1.1 1.0 1.0 1.0 1.0 0.93.9 1.1 1.0 1.0 1.0 1.0 0.94 1.1 1.0 1.0 1.0 1.0 0.9

40

Table 11 14 mm chippings, Emulsion 60% cationic spray rates


Climate




8 2.0 1.9 1.8 1.9 1.8 1.78.1 2.0 1.9 1.8 1.9 1.8 1.78.2 2.0 1.9 1.8 1.9 1.8 1.78.3 2.0 1.9 1.8 1.9 1.8 1.78.4 2.0 1.9 1.8 1.9 1.8 1.78.5 2.0 1.9 1.8 1.9 1.8 1.78.6 2.0 1.9 1.8 1.9 1.8 1.78.7 2.0 1.9 1.8 1.9 1.8 1.78.8 2.0 1.9 1.8 1.9 1.8 1.78.9 2.0 1.9 1.8 1.9 1.8 1.79 2.0 1.9 1.8 1.9 1.8 1.79.1 2.0 1.9 1.8 1.9 1.8 1.79.2 2.1 2.0 1.9 2.0 1.9 1.89.3 2.1 2.0 1.9 2.0 1.9 1.89.4 2.1 2.0 1.9 2.0 1.9 1.89.5 2.1 2.0 1.9 2.0 1.9 1.89.6 2.1 2.0 1.9 2.0 1.9 1.89.7 2.1 2.0 1.9 2.0 1.9 1.89.8 2.1 2.0 1.9 2.0 1.9 1.89.9 2.1 2.0 1.9 2.0 1.9 1.810 2.1 2.0 1.9 2.0 1.9 1.8

41



Climate




5 1.7 1.6 1.6 1.6 1.6 1.55.1 1.7 1.7 1.6 1.7 1.6 1.55.2 1.7 1.7 1.6 1.7 1.6 1.55.3 1.8 1.7 1.6 1.7 1.6 1.55.4 1.8 1.7 1.6 1.7 1.6 1.55.5 1.8 1.7 1.6 1.7 1.6 1.55.6 1.8 1.7 1.6 1.7 1.6 1.55.7 1.8 1.7 1.6 1.7 1.6 1.55.8 1.8 1.7 1.6 1.7 1.6 1.55.9 1.8 1.7 1.6 1.7 1.6 1.56 1.8 1.7 1.6 1.7 1.6 1.56.1 1.8 1.7 1.6 1.7 1.6 1.56.2 1.8 1.7 1.6 1.7 1.6 1.66.3 1.8 1.7 1.7 1.7 1.7 1.66.4 1.8 1.7 1.7 1.7 1.7 1.66.5 1.8 1.8 1.7 1.8 1.7 1.66.6 1.9 1.8 1.7 1.8 1.7 1.66.7 1.9 1.8 1.7 1.8 1.7 1.66.8 1.9 1.8 1.7 1.8 1.7 1.66.9 1.9 1.8 1.7 1.8 1.7 1.67 1.9 1.8 1.7 1.8 1.7 1.6

42



Climate




2 1.5 1.4 1.4 1.4 1.4 1.32.1 1.5 1.4 1.4 1.4 1.4 1.32.2 1.5 1.4 1.4 1.4 1.4 1.32.3 1.5 1.4 1.4 1.4 1.4 1.32.4 1.5 1.5 1.4 1.5 1.4 1.32.5 1.5 1.5 1.4 1.5 1.4 1.32.6 1.5 1.5 1.4 1.5 1.4 1.32.7 1.6 1.5 1.4 1.5 1.4 1.32.8 1.6 1.5 1.4 1.5 1.4 1.32.9 1.6 1.5 1.4 1.5 1.4 1.33 1.6 1.5 1.4 1.5 1.4 1.33.1 1.6 1.5 1.4 1.5 1.4 1.33.2 1.6 1.5 1.4 1.5 1.4 1.43.3 1.6 1.5 1.4 1.5 1.4 1.43.4 1.6 1.5 1.4 1.5 1.4 1.43.5 1.6 1.5 1.5 1.5 1.5 1.43.6 1.6 1.5 1.5 1.5 1.5 1.43.7 1.6 1.6 1.5 1.6 1.5 1.43.8 1.6 1.6 1.5 1.6 1.5 1.43.9 1.6 1.6 1.5 1.6 1.5 1.44 1.7 1.6 1.5 1.6 1.5 1.4

43

Table 14 Spread rate and coverage of chippings

Area Area Area Areacovered covered covered covered

by one by one by one by oneSpread ‘spot’ of Spread ‘spot’ of ‘spot’ of ‘spot’ of

ALD rate chippings ALD rate chippings ALD chippings ALD chippingsmm kg/m2 m2 mm kg/m2 m2 mm kg/m2 m2 mm kg/m2 m2

10 13.6 10.4 8 10.9 13 6 8.2 17.3 4 5.5 25.89.9 13.5 10.5 7.9 10.8 13.1 5.9 8 17.7 3.9 5.3 26.79.8 13.4 10.6 7.8 10.6 13.4 5.8 7.9 17.9 3.8 5.2 27.39.7 13.2 10.7 7.7 10.5 13.5 5.7 7.8 18.2 3.7 5 28.49.6 13.1 10.8 7.6 10.4 13.6 5.6 7.6 18.7 3.6 4.9 28.99.5 13 10.9 7.5 10.2 13.9 5.5 7.5 18.9 3.5 4.8 29.59.4 12.8 11.1 7.4 10.1 14 5.4 7.4 19.2 3.4 4.6 30.89.3 12.7 11.2 7.3 10 14.2 5.3 7.2 19.7 3.3 4.5 31.59.2 12.5 11.3 7.2 9.8 14.5 5.2 7.1 20 3.2 4.4 32.29.1 12.4 11.4 7.1 9.7 14.6 5.1 7 20.3 3.1 4.2 33.89 12.3 11.5 7 9.5 14.9 5 6.8 20.8 3 4.1 34.68.9 12.1 11.7 6.9 9.4 15.1 4.9 6.7 21.2 2.9 4 35.48.8 12 11.8 6.8 9.3 15.2 4.8 6.5 21.7 2.8 3.8 37.38.7 11.9 11.9 6.7 9.1 15.6 4.7 6.4 22.1 2.7 3.7 38.38.6 11.7 12.1 6.6 9 15.8 4.6 6.3 22.6 2.6 3.5 40.58.5 11.6 12.2 6.5 8.9 15.9 4.5 6.1 23.1 2.5 3.4 41.78.4 11.5 12.3 6.4 8.7 16.3 4.4 6.0 23.6 2.4 3.3 438.3 11.3 12.5 6.3 8.6 16.5 4.3 5.9 24.2 2.3 3.1 45.78.2 11.2 12.7 6.2 8.5 16.7 4.2 5.7 24.7 2.2 3 47.38.1 11 12.9 6.1 8.3 17.1 4.1 5.6 25.3 2.1 2.9 48.9

44

SINGLE SURFACE DRESSING

Preparation Notes

1 Calculate area of section to be treated. Area = section length × section width

2 Decide area of surface to be preparedthat day.

3 Sweep clear loose material andexcess dust.

4 Fill in depressions and holes in surfacewith gravel and compact.

5 Sweep clear repaired areas.

6 Lightly apply water to preparedsurface area. Watering cans may be used.

7 Prime surface to be treated. Apply prime by hand sprayer.

Construction Notes

1 Mark out area of road surface to be Use a string line.treated in one day into sections.

2 Place chippings at set intervals along See Table 14.either side of the road to be treated usinghalf 210 litre drums with the bottom ofthe drum removed.

3 Construct a small windrow along the edges Sand and gravel or rope may be used.of road to mark the limit of the area ofsurface to be sprayed and to contain anyrunoff of emulsion.

4 If it is to be used as the binder, arrange for The heating of MC3000 must be done in athe heating of MC3000 cut-back bitumen. tractor drawn heater tank fitted with a dieselHeat to 155

oC or if a thermometer is not fuelled burner and a hand lance sprayer fitted.

available, until the binder steams andflows very easily.

5 If watering cans are to be used withemulsion, measure the volume ofwatering cans.

Continued ....

45

SINGLE SURFACE DRESSING (Continued)

Construction Notes

6 Apply MC 3000 or emulsion binder tothe surface area by hand lance sprayer.

or

7 Emulsion can be applied using watering Do not attempt to apply MC3000 withcans and spread over area with brooms watering cans.and brushes after application.

8 Immediately after the binder has been Prevent traffic or pedestrians entering thespread, apply the chippings using hand construction area until after the binder andshovels. chippings have been spread. Use a broom

to help ensure even distribution.

9 Roll the surface Begin as soon as chippings have beenapplied to binder.

10 Continue 6 - 9 until the area of the Continue rolling for as long as possible.road to treat that day has been completed. 2 hours minimum as a guide. Very slow

moving traffic may be allowed onto thesurface during rolling.

11 When the surface is stable, remove Sweep the surface in the cool of earlyexcess chippings. morning. Retain excess chippings for use

elsewhere.

12 Finish the surface treatment by applying Follow the construction details froma sand seal. page 30.

46

Plate 12 Brooming of surface

Plate 13 Application of binder using watering can

Plate 14 Pedestrian roller

47

48

12 Double surface dressing

Description of treatmentA bituminous seal consisting of two layers of bituminous binder and twolayers of single size stone chippings. The size of the second layer of chippingsis roughly half that of the first layer. A combination of chipping sizes thatwould meet this requirement are a first layer of nominal 14 mm chippingsfollowed by a second layer of 6 mm chippings.

Bituminous binder Spray rate1st layer and 2nd layer

MC3000 cut-back See Tables 8 - 10

Emulsion, 60% cationic See Tables 11 - 13

Chipping spread rate See Table 14

Equipment and tools


� String.

� Shovels.

� Rakes.

� Brooms.

� Hand sprayer or watering cans for emulsion only.

� Safe method for the heating of MC3000.

� Buckets.

� Tamping tool.

� Squeegees.

� Pedestrian roller or tractor.

Materials

� Water.

� MC30 cut-back bitumen or invert emulsion prime.

� MC3000 cut-back bitumen or bituminous emulsion.

� Nominal single size stone chippings.

49

DOUBLE SURFACE DRESSING

Preparation Notes

1 Calculate area of section to be treated. Area = section length × section width

2 Decide area of surface to be preparedthat day.

3 Sweep clear loose material and excessdust.


5 Sweep repaired areas

6 Lightly apply water to prepared Watering cans may be used.surface area.


Construction (1st layer) Notes

1 Mark out area of road surface to be Use a string line. treated in one day into sections.

2 Place chippings at set intervals along See Table 14.either side of the road to be treatedusing half 210 litre drums with thebottom of the drum removed.

3 Construct a small windrow along the Sand and gravel or rope may be used.edges of road.

4 If it is to be used as the binder, arrange The heating of MC3000 must be done in afor the heating of MC3000 cut-back tractor drawn heater tank fitted with a dieselbitumen. Heat to 155

oC or if a fuelled burner and a hand lance sprayer

thermometer is not available, until the fitted.binder steams and flows very easily.

5 If watering cans are to be used withemulsion, measure the volume ofwatering cans.

Continued ....

50

DOUBLE SURFACE DRESSING (Continued)

Construction (1st layer) Notes

6 Apply MC3000 or emulsion binderto the surface area by hand lance sprayer.

or

7 Emulsion can be applied using watering Do not attempt to apply MC3000 withcans and spread over area with brooms watering cans.and brushes after application.

8 Immediately after the binder has been Prevent traffic or pedestrians entering thespread, apply chippings onto top of construction area until after the binder andbinder using hand shovels. chippings have been spread. Use a broom to

help ensure even distribution.

9 Roll the surface. Begin as soon as chippings have beenapplied to binder.

10 Continue 6 - 9 until the area of the road Continue rolling for as long as possible.to treat that day has been completed. 2 hours minimum as a guide. Very slow

moving traffic may be allowed onto thesurface during rolling.

11 When the surface is stable, remove Sweep the surface in the cool of earlyexcess chippings. morning. Retain excess chippings for

elsewhere.

Construction 2nd layer Notes

1 Prepare the existing chipping layer by 2 to 3 months after construction of 1st layer.sweeping clear any loose material.

2 Mark out area of road surface to be Use a string line.treated in one day into sections.

3 Continue to follow stages 2 - 11 asbefore for the construction of the 1st layer.

51

Plate 15 Sweeping excess chippings

52

13 Single Otta seal

Description of treatmentA bituminous surfacing layer approximately 16 mm thick made up of gradedaggregate from natural gravel or crushed rock in combination with a softbituminous binder. It is suitable for roads and tracks carrying less than 500vehicles per day.

Bituminous binder Spray rateMC3000 cut-back. 2.0 l/m2

Minimum 200 penetration grade

bitumen based emulsion, HFMS-2s,

ASTM specification D2397. 2.4 l/m2

Screened gravel spread rate See Table 4, page 16.


� Buckets.

� Tamping tool.

� Squeegees.

� 12 tonne pneumatic roller (ifavailable) or pedestrian roller andheavily loaded lorry.

Equipment and tools


� String.

� Shovels.

� Rakes.

� Brooms.

� Hand lance sprayer.

Materials

� Water.


� MC3000 cut-back bitumen orHFMS-2s emulsion.

� Screened gravel.

53

SINGLE OTTA SEAL

Preparation Notes

1 Decide the area of surface to be Area = section length × section width.prepared that day.

2 Sweep clear loose material andexcess dust.


4 Sweep repaired areas.

5 Lightly apply water to prepared Use watering cans.surface area.

6 Prime surface to be treated. Apply prime by hand sprayer at rate of1.0 - 1.2 litres per square metre.

Construction Notes

1 Mark out area of road surface to betreated in one day with a string lineinto 5 metre sections.

2 Calculate area of first 5 metre length Area (m2) = 5 × width of road.section to be treated.

3 Place aggregate at set intervals along See Table 5, page 17.either side of the road to be treatedusing half 210 litre drums with thebottom of the drum removed.

4 Using sand or gravel, construct a small Rope may be used as a substitute.windrow along the edges of the areato be treated.

5 Construct surface treatment in 5 metre No more than 3.5 metre wide sections.length sections.

6 Arrange for the heating of MC3000 The heating of MC3000 must be done in acut-back bitumen. Heat to 155

oC or if tractor drawn heater tank fitted with a diesel

a thermometer is not available, until fuelled burner and a hand lance sprayerthe binder steams and flows very easily. fitted.

Continued ....

54

SINGLE OTTA SEAL (Continued)

Construction Notes

7 Apply correct binder spray rate to thesurface area by hand sprayer.

8 Spread binder over area with brushesafter application by watering cans.

9 Immediately after the binder has been Be sure to prevent traffic or pedestriansspread, apply graded gravel onto top of entering the construction area until after thebinder using hand shovels. binder and aggregate has been spread.

10 Roll the gravel surface Begin as soon as gravel has been applied tobinder.

11 Repeat 8 to 10 until the area of the road Continue rolling for as long as possible.to treated that day has been completed. 2 hours minimum as a guide. Traffic may be

allowed onto the surface during rolling.

12 Remove excess gravel. Sweep surface clear of excess gravel after aperiod of 1 week. Retain gravel to be usedelsewhere.

55

56

14 Double Otta seal

Description of treatmentSuitable for roads and tracks carrying more than 500 vehicles per day. In thisrespect, this treatment is not strictly necessary for low-volume roads. It isincluded in the manual to mirror the application of double surface dressing, aseal that is recommended for the upgrading of unpaved roads. A double Ottaseal is two bituminous surfacing layers approximately 32 mm thick in total,made up of graded aggregate from natural gravel or crushed rock incombination with a soft bituminous binder.

Bituminous binder Spray rate1st layer 2nd layer

MC3000 cut-back bitumen. 1.8 l/m2 2.0 l/m2

Minimum 200 penetration grade

bitumen based emulsion, HFMS-2s,

ASTM specification D2397. 2.4 l/m2 2.4 l/m2

Screened gravel spread rate See Table 4, page 16.


� Buckets.

� Tamping tool.

� 12 tonne Pneumatic roller (ifavailable) or pedestrian roller andheavily loaded lorry.

Equipment and tools


� String.

� Shovels.

� Rakes.

� Brooms.

� Hand lance sprayer.

Materials

� Water.


� MC3000 cut-back bitumen orHFMS-2s emulsion.


57

DOUBLE OTTA SEAL

Preparation Notes

1 Decide area of surface to be prepared Area = section length × section width.that day.




5 Lightly apply water to prepared surface Use watering cans.area.


Construction 1st layer Notes

1 Mark out area of road surface to betreated in one day with a string lineinto 5 metre sections.

2 Calculate area of first 5 metre length Area (m2) = 5 × width of roadsection to be treated.

3 Place aggregate at set intervals at either See Table 5, page 17.side and along the side of the road to betreated using half 210 litre drums withthe bottom of the drum removed.

4 Using sand or gravel, construct a small This is to prevent overspray of binder.windrow along the edges of the area tobe treated.

5 Construct surface treatment in 5 metre No more than 3.5 metre wide sections.length sections.

6 Arrange for the heating of MC3000 The heating of MC3000 must be done in acut-back bitumen. Heat to 155oC or if tractor drawn heater tank fitted with a diesela thermometer is not available, until the fuelled burner and a hand lance sprayerbinder steams and flows very easily. fitted.

Continued ....

58

DOUBLE OTTA SEAL (Continued)

Construction 1st layer Notes

7 Apply correct binder spray rate to thesurface area by hand sprayer.

8 Spread binder over area with squeegeesafter application by watering cans.

9 Immediately after the binder has been Be sure to prevent traffic or pedestrianssprayed, apply graded gravel onto the entering the construction area until after thetop of binder using hand shovels. binder and aggregate has been spread.

10 Roll the gravel surface. Begin as soon as gravel has been applied tobinder.

11 Repeat 8 to 10 until the area of the road Continue rolling for as long as possible.to be treated that day has been completed. 2 hours minimum as a guide. Any traffic

may be allowed onto the surface duringrolling.

12 Remove excess gravel. Sweep surface clear of excess gravel after aperiod of 1 week. Retain gravel to be usedelsewhere.

Construction of 2nd layer 2 to 3 months after construction of 1st layer

1 Sweep clear all loose material and excess Construct the 2nd layer in the same way asdust from the first Otta seal layer. the 1st by following stages 1 - 12.

59

60

15 Pre-mixed bitumen and gravel

Description of treatmentA material made up of washed natural gravel coated with bitumen emulsionthat is laid immediately after mixing to a thickness of approximately 40 mmwhile the emulsion is in an unbroken state.

Bituminous binder Application rateEmulsion, (60% slow setting grade). 2 litres per 25kg gravel

Aggregate 1 cubic metre is approximately230kg.

� Concrete mixer.

� Wheelbarrows.

� Buckets.

� Tamping tool.


� Wooden batons approximately40 mm thick.

Equipment and tools

� Measuring tape of minimum10 metre length.

� String.

� Shovels.

� Rakes.

� Brooms.

� Hand sprayer or watering cans.

Materials

� Water.


� Stable grade emulsion.


61

PRE-MIXED BITUMEN AND GRAVEL

Preparation Notes

1 Define area of surface to be preparedthat day.




5 Lightly apply water to prepared surfacearea.

6 Prime surface to be treated.

7 Mark out area of surface to be treated 24 hours after priming.and place wooden batons at the sidesof this area.

Mixing Notes

Mechanical mixing method. Dirt and mud must not be carried by thewheelbarrows onto the surface to be treated.

1 Start the concrete mixer rotating. Any standard concrete mixer may be used.

2 Add a portion of the emulsion first to To prevent aggregate clinging to the bottomthe mixer. of the mixer.

3 Add the amount of aggregate suitablefor the size of mixer in use.

4 Add the rest of the emulsion. If the aggregate contains a large amount offines then more water should be added tothe mix.

5 Mix for a short time. The time of mixing should only be for aslong as to fully coat the aggregate.Prolonged mixing will strip the emulsionfrom the aggregate.

Continued ....

62

PRE-MIXED BITUMEN AND GRAVEL (Continued)

Mixing Notes

Hand mixing method.

1 Pre-mixed bitumen and gravel may In hand mixing the emulsion is poured overbe made by fully manual methods. the aggregate, which is turned over by

shovels until coating is complete.

Spreading and placing Notes

1 Discharge the mixture into wheelbarrows.

2 Empty the barrow loads of premix ontothe road surface between wooden batons.

3 Spread the pre-mix over the surface to the See Plate 16.depth of the wooden batons (40 mm) with Take care to avoid segregation of therakes and shovels. aggregate. During the operation, the tools

must be dipped into water and wiped cleanto prevent build up of material.

4 Wait until the emulsion in the pre-mix hasbroken to the full depth of the layer.

5 Roll the spread premix with a pedestrian Water may be sprayed onto the roller drumroller. to act as a lubricant.

6 Spread coarse sand over the rolled pre-mix. A seal of bitumen and crusher dust or sandwill give a more waterproof surface.

7 No traffic is to be allowed on the surfaceon the day of construction.

8 When work has finished for the day, Wheelbarrow operators to be responsible.barrows must be cleaned of anyremaining pre-mix.

63

Plate 16 Placing of material between wooden batons

64

16 Penetration macadam

Description of treatment

Construction using coarse followed by smaller coarse aggregate, penetratedin-situ by a bituminous binder then thoroughly rolled.

Bituminous binder Application rateRapid setting emulsion. 5.5 - 7.0 litres/m2

Aggregate FormationNominal single sized material. 60% of 40 mm

30% of 28 mm10% of 14 mm - 20 mm

Equipment and tools


� String.

� Shovels.

� Rakes.

� Brooms.

� Watering cans.

� Wheelbarrows.

� Buckets.

� Tamping tool.

� 8 tonne roller.

Materials

� Water.

� Cationic rapid break emulsion.

65

PENETRATION MACADAM

Preparation Notes

1 Define area of surface to be preparedthat day.




Construction Notes

1 Unload aggregate outside the area ofroad to be treated.

Ensure aggregate does not becomecontaminated with dirt and dust.

2 Lay the 40 mm aggregate on the road Aggregate may be laid by hand.surface. See Plate 17.

3 Lay the 28 mm aggregate.

4 Lay the 14 mm-20 mm aggregate.

5 Roll and compact the aggregate. Rolling should begin from the edges of theroad and work towards the centre.

Continue rolling until no movement of theaggregate is seen. See Plate 18.

6 Dampen the surface of the aggregate. See Plate 19.

7 Apply emulsion to the newly rolled Apply with watering cans. See Plate 20.surface at the required rate.

66

Plate 17 Largest aggregate placed by hand

Plate 18 Compacted surface

67

Plate 19 Aggregate damping by hand

Plate 20 Application of emulsion binder

68

17 Maintenance

Whichever bituminous surface has been constructed it is essential the roadsurface, shoulders and adjacent land be inspected at regular times so that anyfailures can be identified and repaired by appropriate maintenance. Theoutcome of failing to carry out maintenance will almost certainly lead tocommon failures in the surface of the road that must be repaired, includecracking, rutting, shoving, potholes and edge damage.

It is beyond the scope of this manual to describe all the possible failures anddefects that may occur but attention should be given to the condition ofshoulders and roadside areas with respect to drainage. It is essential tomaintain the adequate drainage of water from the road surface to keep the roadstructure and surface sound. Therefore, attention and maintenance should beapplied to the drainage system including ditches, pipedrains and culverts.Some common problems and suggested remedies are as follows.

Obstructions on road shoulders.These cause slowing or prevention of surface water flowing from the roadsurface therefore obstructions should be removed.

The level of the shoulders becomes higher than level of road.

This results in water ponding at the edges of the road surface, causingweakening of the underlying layers of the road. The maintenance action is toreshape and remove material from the shoulders to the correct level and toclear any excess vegetation that may be contributing to the problem.

The level of the shoulders becomes lower than the level of the road with rutsand depressions.

Not enough support is given to the road and the shoulders become softallowing edge breaks from the road. Material should be added to the shouldersand compacted back to the level of the road pavement.

Obstructions in ditches and drainsGrowths of vegetation, fallen trees, loose silt or rock cause blockage of theditch. The ditch should be cleared and cleaned.

SiltingCaused by water flowing too slowly leading to blockage of the ditch. Theditch should be deepened.

69

Ponding of water in ditches and on the shoulders.The ditch cross-section is too small or the gradient of the ditch is too flat. Ifleft alone the shoulder material will become soft and can erode. In extremecases the road can be flooded leading to weakening of the pavement layer. Theditches should be deepened and new turn out drains constructed.

70

Appendix A: Worked examples

PrimingAn unpaved road, 100 metres long and 3.5 metres wide, within a village, is tobe treated with a sand seal. The track is to be primed using an invert emulsionand applied with a hand lance.

1 Calculate the spray delivery rate of the hand lance by timing how long ittakes to fill a 10 litre container.

2 Time to fill container = 65 seconds.

3 Therefore delivery spray rate = 10 litres ÷ 65 seconds = 0.154 litres persecond.

4 Application spray rate of invert emulsion = 1.2 litres per square metre.

5 Mark out the length of the track using string or other means into convenientlength sections, for example 5 metre long sections.

6 Each section therefore covers an area of 5 × 3.5 = 17.5 square metres.

7 Each section should receive 17.5 × 1.2 = 21 litres of invert emulsion.

8 The time to spray this section area = 21 ÷ 0.154 = 136 seconds.

9 The priming should be carried out by two people pushing the emulsiondrum carrier backwards along the track as the hand lance operator sprayseach 5 metre long section in 136 seconds by spraying from side to side. Atimekeeper calls out the time in intervals to the hand lance operator sochecks on the coverage of emulsion can be made.

10 Stage 9 should be practised on waste ground if operators are new orinexperienced in the use of the hand lance.

71

Sand sealAn unpaved road that carries mainly pedal cycle and pedestrians, 3 metreswide, 500 metres long through a village, is to be sand sealed using labour-based methods. A cationic emulsion is to be used as the bituminous binder.Only watering cans are available.

1 The area of the road should first have been primed and swept clear of anyloose material.

2 Area to be sand sealed = 3 × 500 = 1500 square metres.

3 Binder spray rate = 1.6 litres per square metre.

4 Therefore 1.6 × 1500 = 2400 litres of emulsion required.

5 The watering cans hold 10 litres of emulsion.

6 Therefore 1 watering can will cover 6.25 square metres.

7 Allow 1 watering can of emulsion to be spread by brooms or squeegees to6 square metres of the track.

8 As the track is 3 metres wide, 2 metre lengths can be covered at a time byone watering can.

9 The sand should be applied at 13 to 19 kilograms per square metre.

10 Therefore, 78 to 114 kilograms should be spread over each 6 square metresection.

11 Roll the surface with a pedestrian roller.

72

Slurry sealA 3 metre wide unpaved track along 300 metres of its length is to be slurrysealed using labour-based methods. The mixing of the slurry is to be carriedout by a concrete mixer of 110 litre capacity.

� Area of road to be treated = 3 × 300 = 900 square metres.

� Each batch mix requires amounts of materials as follows.

� Crusher dust = 0.6897 × 110 = 75.9 litres.

� Emulsion = 0.1724 × 110 = 19 litres.

� Water = 0.1149 × 110 = 12.6 litres.

� Cement = 0.0230 × 110 = 2.5 litres.

Half the width of the track will be constructed at a time.

Therefore half the width = 1.5 metres.

To construct a slurry seal of 5 mm thick, each mix of 110 litres will coverapproximately a section length of 14.5 metres and is calculated from,

Width of section = 1.5 metres = 150 centimetres

Slurry seal thickness = 5 mm = 0.5 centimetres

Volume of mixer = 110 litres = 110 × 1000 cubic centimetres

Length = Volume

Width of section Slurry seal thickness×

Length (cms) = 110 1000

150 0.5

××

= =110000

751466 7.

Length (metres) = 1466.7

100= 14 7.

73

Single surface dressingIn a hot and dry climate, 250 metres of a rural road 3.6 metres wide, carrying30 vehicles per day, through a village is to be single surface dressed withangular 10 mm chippings whose ALD has been measured as 6.2 mm. A hand-operated sprayer with a rate of delivery of 0.25 litres per second is availablefor the application of bituminous binders. A 60% bituminous emulsion binderis to be used. Watering cans contain 9 litres. The full width of the road may betreated at once.

Prime

1 Total area of road to be treated is 250 metres × 3.6 metres = 900 squaremetres.

2 Sweep the area clear during the day.

3 Lightly dampen the road surface with water applied by watering cans

4 Prime surface with MC30 cut-back. Apply at 1.0 litres per square metre.

5 Volume of prime needed for 900 square metres = 1.0 × 900 = 900 litres.

6 Total time to spray 900 litres over 250 metres = 900 ÷ 0.25 = 3600 seconds= 60 minutes.

7 To ensure the correct spray rate of prime is applied, the operator of thesprayer should in 1 minute cover (250 ÷ 60) = approximately 4.2 metrelength of the road.

Single surface dressing

1 Chipping spread rate = 8.5 kg/m2 (see Table 14).

2 One ‘spot’ of chippings will cover 16.7 square metres (see Table 14).

3 Length of road one ‘spot’ will cover is 16.7(area) ÷ 3.6(width) = 4.6 metres(approximately 4.5 metres).

4 Therefore ‘spot’ the chippings along the road approximately every4.5 metres

5 For convenience, measure and mark out the first 45 metres of the road to betreated into 4.5 metre length sections.

6 Therefore area of each section = 4.5 × 3.6 = 16.2 square metres.

74

Emulsion binderHot and dry climate Binder spray rate see Table 12.Angular 10 mm chippingsALD = 6.2 mm


8 Volume of binder to spray first section = 16.2 × 1.6 = 25.92 litres.

9 To spray each section, the hand sprayer should apply the binder in25.92 ÷ 0.25 = 103.68 seconds.

Alternatively, if watering cans were used to apply the binder then to covereach section of 16.2 square metres with 25.92 litres would require 2.9watering cans of 9 litre capacity. Therefore,

Apply 3 watering cans of binder to section 1 and spread evenly with brooms.

10 Spread chippings over surface of binder using hand shovels.

11 Repeat the above for section 2,3,4,-,-,-,-,-,10 and begin rolling operationwhen sufficient sections have been treated so the roller is not in the way ofthe spraying and spreading operation.

12 Repeat above sequence until the entire 250 metre length has been treated.

}

75

Double surface dressingIn a hot and dry climate, 450 metres of a rural road 6 metres wide, carrying30 vehicles per day, through a village is to be double surface dressed with14 mm and 6 mm chippings of measured ALD 8.4 mm and 3.4 mmrespectively. The chippings are rounded in shape. A hand-operated sprayerwith a rate of delivery of 0.25 litres per second is available for theapplication of bituminous binders. A 60% bituminous emulsion binder is tobe used. Watering cans contain 9 litres. The two lanes or sides of the roadmust be surface dressed separately.

Prime

1 Total area of road to be treated is 450 metres × 6 metres = 2700 squaremetres.

2 Sweep the area clear during the day.

3 Lightly dampen the road surface with water applied by watering cans.

4 Prime surface of road with MC30 cut-back bitumen. Apply at 1.0 litres persquare metre.

5 Therefore the volume of prime required for 2700 square metres = 1.0 ×2700 = 2700 litres.

6 The total time to spray 2700 litres over the 450 metre length of road, willtake 2700 ÷ 0.25 = 180 minutes.

7 To ensure the correct rate of prime is applied, the operator of the sprayershould in 1 minute cover (450 ÷ 180) = approximately 2.5 metre length ofthe road.

Surface dressing 1st layer

1 Chipping spread rate = 11.5 kg/m2. (see Table 14).

2 Half the width of the road must be treated at a time. Therefore width = 3metres.

3 One ‘spot’ of chippings will cover 12.3 square metres (see Table 14)

4 Length of road one ‘spot’ will cover is 12.3(area) ÷ 3(width) = 4.1 metres(approximately 4 metres).

5 Therefore ‘spot’ the chippings along the road approximately every 4 metres.

6 For convenience, measure and mark out the first 40 metres of the road to betreated into 4 metre length sections.

7 Therefore area of each section = 4.0 × 3.0 = 12.0 square metres

76

Emulsion binderHot and dry climate Binder spray rate see Table 11.Rounded 14 mm chippingsALD = 8.4 mm

Emulsion binder spray rate = 1.9 litres per square metre.


9 The hand sprayer should apply the binder in 22.8 ÷ 0.25 = 91 seconds.

Alternatively, if watering cans were used to apply the binder then to covereach section of 12 square metres with 22.8 litres of binder would require alittle over 2.5 watering cans of 9 litre capacity. Therefore,

Apply 2.5 watering cans of binder to first section and spread evenly withbrooms.

10 Spread chippings over the surface of the binder using hand shovels.

11 Repeat the above for section 2,3,4,-,-,-,-,-,10 and begin rolling operationwhen sufficient sections have been treated so roller is not in the way of thespraying and spreading operation.

12 Repeat above sequence until entire 450m has been treated.

13 Repeat 1 to 12 for the other side of the road.

Surface dressing 2nd layer applied 3 months after 1st layer.

1 Chipping spread rate = 4.6 kg/m2 (see Table 14).

2 One spot of chippings will cover = 30.8 square metres (see Table 14).

3 Half the width of the road must be treated at a time. Therefore width = 3metres.

4 Length of road one ‘spot’ will cover = 30.8(area) ÷ 3(width) = 10.3 metres(approximately 10 metres).

5 Therefore ‘spot’ the aggregate on either side and along the road every 10metres.

6 For convenience, measure and mark out the first 100 metres of the road tobe treated into 10 metre sections.

7 Therefore area of each section = 10 × 3.0 = 30 square metres

}

77

Emulsion binderHot and dry climate Binder spray rate see Table 13.Rounded 6 mm chippingsALD = 3.4 mm

8 Emulsion binder spray rate = 1.5 litres per square metre.

9 Volume of binder to cover first section = 30 × 1.5 = 45 litres.

10 The hand sprayer should apply the binder in 45 ÷ 0.25 = 180 seconds.

Alternatively, if watering cans were used to apply the binder then to covereach section would require 5 watering cans of 9 litre capacity. Therefore,

Apply 5 watering cans of binder to first section and spread evenly withbrushes.

11 Spread chippings over the surface of the binder using hand shovels.

12 Repeat the above for section 2,3,4,-,-,-,-,-,10 and begin rolling operationwhen sufficient sections have been treated so roller is not in the way of thespraying and spreading operation.

13 Repeat above sequence until the entire 450m has been treated.

14 Repeat 1 to 12 for the other side of the road.

}

78

Single Otta seal250 metres of rural road 3.5 metres wide, carrying 20 vehicles per day,running through a village is to be treated with a single Otta seal. A hand-operated sprayer with a rate of delivery of 0.3 litres per second is available forthe application of bituminous binders. MC3000 cut-back bituminous binder isto be heated by a tractor drawn heater tank fitted with a diesel fuelled burner.A road diversion is possible and therefore the entire width of the road may betreated at once.

1 Total area of the road to be treated = 3.5 metres × 250 metres = 875 squaremetres.

2 The 250 metre length of road is marked out into 5 metre long sections = 50sections.

3 Each section is therefore = 17.5 square metres.

Prime

1 The rate of spray of the MC30 prime = 1.0 litres per square metre.

2 Therefore each 5 metre section will need = 17.5 × 1.0 = 17.5 litres MC30.

3 The time to spray this amount with the hand sprayer with a rate of deliveryof 0.3 litres per second = 17.5 ÷ 0.3 = 58.3 seconds.

4 The time to prime the 250 metre length of the road = 48.6 minutes in total.

Single Otta seal

1 Aggregate spread rate = 10 - 11 kg/m2 (see Table 4).

2 One ‘spot’ of aggregate will cover 7.5 square metres (see Table 4).

3 Length of road one ‘spot’ will cover is 7.5(area) ÷ 3.5(width) = 2.1 metres.

4 Spot the aggregate along the road every 2 metres (see Table 5).

5 For convenience, measure and mark out the first 20 metres of the road to betreated into 2 metre length sections.

6 Therefore area of each section = 3.5 × 2 = 7.0 square metres.


8 Volume of binder to spray each section = 7.0 × 2.0 = 14.0 litres.

9 The hand sprayer should apply the binder in 14.0 ÷ 0.3 = 46.7 seconds.

79

Alternatively, if watering cans were used to apply the binder then to covereach section of 7.0 square metres would require approximately 1.5 wateringcans of 10 litre capacity. Therefore,

Apply 1.5 watering cans of binder to first section and spread evenly withbrushes.

10 Spread aggregate over the surface of the binder using hand shovels.

Repeat the above for the following sections and begin rolling operation whensufficient sections have been treated so roller is not in the way of the sprayingand spreading operation.

Repeat above sequence until the entire 250 metre length of the road has beentreated.

80

Double Otta seal

1st layerIf the road previously described in the construction of a single Otta seal was tohave been treated with a double Otta seal, then first a single Otta seal shouldbe constructed as before except the rate of spray of MC3000 for the first layeris 1.8 l/m2.

2nd layer

1 Begin construction two or three months after the construction of the singleOtta seal.

2 Sweep clear loose gravel from surface.

3 The stages of construction are the same as for the single Otta seal except,



6 The hand sprayer should apply the binder in 14.0 ÷ 0.3 = 46.7 seconds.

7 Alternatively, if watering cans were used to apply the binder then to covereach section of 7.0 square metres would require approximately 1.5watering cans of 10 litre capacity.

8 Apply 1.5 watering cans of binder to first section and spread evenly withbrushes.

9 Spread aggregate over the surface of the binder using hand shovels.

10 Repeat the above for the following sections and begin rolling operationwhen sufficient sections have been treated so roller is not in the way of thespraying and spreading operation.

11 Repeat above sequence until the entire 250 metre length of one side of theroad has been treated.

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Pre-mixed bitumen and gravelAn unpaved road, 6 metres wide, that approaches a bridge down a short hill of30 metres in length is to be improved by surfacing with pre-mixed bitumenand gravel to a depth of 40 mm. A stable grade emulsion (CSS60) is chosen asthe bituminous binder.

1 The road surface is prepared by reshaping and compaction and is primedbefore the start of construction of the pre-mixed bitumen and gravelsurface.

2 Aggregate that is to be used as the gravel is screened to remove largestones greater than 12 mm in size.

3 The area of the road to be surfaced is 6 metres × 30 metres = 180 squaremetres. 90 square metres each side of the road.

4 Therefore, the volume of gravel needed for one side of the road is,

9040

10003 6× = . cubic metres

5 1 cubic metre of gravel weighs approximately 230 kilograms.

6 Therefore, the total weight of gravel needed is 230 × 3.6 = 828 kilograms.Each mix contains 150 kilograms of gravel.

7 For one side of the road, 5.5 mixes are needed in total.

8 The aggregate is moistened slightly before mixing with the emulsion in anordinary rotary concrete mixer of 200 litre capacity.

9 2 litres of emulsion are mixed with every 25 kilograms of aggregate.

10 The mixer is run a short time until the emulsion has coated all of theaggregate.

11 The mixture is then loaded into wheelbarrows and spread with steel rakesbetween wooden batons of 40 mm depth.

12 The pre-mix is then rolled.

13 Steps 9 - 12 are repeated for the other side of the road.

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Penetration macadamA parking area for heavy trucks is on an unpaved surface, 6 metres wide, 50metres in length. It is to be improved by surfacing with Penetration Macadam.A rapid break cationic emulsion (CRS60) is chosen as the bituminous binder.

Reshape and compact the existing surface. Priming is not required for thisconstruction method.

Area to be constructed = 6 metres × 50 metres = 300 square metres.

Binder application rate = 7 litres per square metre.

Amount of emulsion required in total = 7 × 300 = 2100 litres.

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Appendix B: Design of surface dressing

The average least dimension (ALD) of a representative sample of some 200chippings each is taken from stockpiles of screened aggregate.

Adjustment weighting factors, see Table B1, are used to match the conditionsfound at the construction site and overall weighting factor is calculated (F)from them. An example is shown in Table B2 where F is calculated for singleand double dressings.

Using the ALD and ‘F’ values in equation B1 gives the required basic rate ofspray of binder in terms of MC3000.

R = 0.625 + (F×0.023) + [0.0375 + (F×0.0011)]×ALD (B1)

Where F = Overall weighting factor

ALD = the average least dimension of the chippings

R = Basic rate of spray of bitumen.

If emulsion is used as the binder then the basic rate of spray of binder is givencalculating R × (90/%bitumen).

ExampleUsing the ALD values of 4.9 mm and 2 mm and the F factors from Table B2,for a single or first dressing, the rate of spray for MC3000 is 1.09 kg/m2 or1.64 kg/m2 for emulsion containing 60 per cent bitumen. For the seconddressing, the rate of spray for MC3000 is 0.9 kg/m2 or 1.35 kg/m2 for emulsioncontaining 60 per cent bitumen.

In the design, there is also an option to increase the bitumen application rateby 8 per cent to ensure that the maximum durability is obtained on low trafficvolume roads.

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Table B1 Weighting factors for surface dressing design

Property Description Factor

Total traffic (all motorised Vehicles/lane/dayclasses) Very light 0 - 50 +3

Light 50 - 250 +1Medium 250 - 500 0Medium-heavy 500 - 1500 -1Heavy 1500 - 3000 -3Very heavy 3000+ -5

Existing surface Untreated or primed base +6Very lean bituminous +4Lean bituminous 0Average bituminous -1Very rich bituminous -3

Climatic conditions Wet and cold +2Tropical (wet and hot) +1Temperate 0Semi-arid (hot and dry) -1Arid (very dry and very hot) -2

Type of chippings Round/dusty +2Cubical 0Flaky -2Pre-coated -2

Table B2 Adjustment factors for single and double surface dressings

First or single dressing Second dressing

Traffic Very light +3 Very light +3

Surface condition Primed roadbase +6 Very lean bituminous +4

Climate Hot and wet +1 Hot and wet +1

Type of chippings Cubical 0 Cubical 0

Total, ‘F’ Factor +10 +8

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Rate of deliveryLitres per second

Time to fillcontainer 10 litre 5 litre(Seconds) container container

30 0.333 0.16731 0.323 0.16132 0.313 0.15633 0.303 0.15234 0.294 0.14735 0.286 0.14336 0.278 0.13937 0.270 0.13538 0.263 0.13239 0.256 0.12840 0.250 0.12541 0.244 0.12242 0.238 0.11943 0.233 0.11644 0.227 0.11445 0.222 0.11146 0.217 0.10947 0.213 0.10648 0.208 0.10449 0.204 0.10250 0.200 0.10051 0.196 0.09852 0.192 0.09653 0.189 0.09454 0.185 0.09355 0.182 0.09156 0.179 0.08957 0.175 0.08858 0.172 0.08659 0.169 0.08560 0.167 0.083

Appendix C: Hand lance delivery spray rates

Rate of delivery (litres per second) =Volume of containerTime to fill container

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